Automatic selector mechanism



July 15, 11952 w. L. WORTHEN 2,603,329

AUTOMATIC SELECTOR MECHANISM Filed Sept. 23, 1946 5 Sheets-Sheet l gwuemfov Jufiy 15, 1952 w. L. WQRTHEN 2,603,329

AUTOMATIC SELECTOR MECHANISM Filed Sept. 23, 1946 5 Sheets-Sheet 2 FIG.2

gwumvhom WILL 1AM L. WORTHEN y 5 9 w. 1.. WORTHEN zmssz AUTOMATIC SELECTOR MECHANISM Filed Sept. 23, 1946 5 Sheets-Sheet 3 FlG.3b

WILLIAM L.WORTHEN Jufly 115, 1952 w. L. WORTHEN AUTOMATIC SELECTOR MECHANISM 5 Sheets-Sheet 4 Filed Sept. 25, 1946 WILLIAM L.WORTHEN fiuly 1,, 1952 w. L. WORTHEN AUTOMATIC SELECTOR MECHANISM 5 Sheets-Sheet 5 Filed Sept. 23, 1946 37Wn(00 WILLIAM L. WORTHEN b 1:! Saw Patented July 15, 1952 AUTOMATIC SELECTOR MECHANISM William L. Worthen, Washington, D. 0., assignor to Melpar, 1110., Washington, D. 0., a corporaticn of New York Application September 23, 194 6, Serial No. 698,607

This invention relates generally tocontrol devices and more particularly to devices for controlling the' positions of one or more shafts from a remote point.

It is an object of the invention to provide a shaft positioning system of simplified character, which shall lend itself to fabrication inextremely compact form.

' It is a further object of the invention to provide a shaft-positioning system which shall be capable of positioning a plurality of shafts under the control of a selecting operation, each of the shafts being independently actuated to one of a plurality of preselected positions, in response to each of the selecting operations.

It is still a further object of the invention to provide a shaft positioning system of extreme accuracy, and which shall be adapted for con trolling tuning devices and control devices associated-with radio transmitters and the like, to enable operation thereof at any one of a plurality 7 Claims. (Cl. 192-142) 2 Figurel is'a wiring diagramof the illustrated embodiment ofthe invention. 7

Figure 5 is a view in perspective of a control and protective switching arrangement illustrated in schematic fashion in the wiring diagram of Figure 4; and r s Figure '6 is a perspective view of a zero stop device of novel-construction and which forms part of the mechanism of the invention.

Briefly described, the present invention is adapted to position each of a plurality of shafts to preselected positions in response to control action of a selector switch. The system is soarranged that the position of each of the plurality of shafts, in response to selection of any switch position, is independent of the positions of the remaining shafts. Each shaft may be positioned selectively to any one of a plurality of positions,

of predetermined frequencies, in accordance with e a selection operation performed remotely from the said transmitter.

Stilla further object of the invention resides in the provision of a-remote tuning and control system of novel construction for radio equipment in general, and for radio transmitters in particular.

It is another object of the invention-to provide a system of the above character which is-particularly adapted for compactness and lightness of construction not only without sacrifice of accuracy and reliability of results but with a marked increase in these desirable qualities.

Still further objects and advantages of the invention will become apparent upon study of the following detailed description of a particular'embodiment thereof, when taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a perspective view of a complete shaft positioning device constructed in accordance with the invention, and with certain parts cut away or removed to clarify the overall construction.

Figure 2 is a sectional view taken axially through a shaft selecting cylinder, and showing de'tails'of construction of shaft position selecting cams, and of associated stop rings and control pawls therefor.

Figure 3a is a perspective view showing, in assembly, a plurality of shaft position stop rings. locking devicesassociated with the rings, and selector cams for the locking devices.

Figure 3b is. a view taken in transverse section through the assembly of Figure 3a.

and the positions may be preselected or predetermined readily and by an extremely simple operation, and modified whenever and as desired.

In the present embodiment of the invention provision is made for a total of ten predetermined shaft positions, in response to the selection of ten control switch positions. Additionally, means are provided in response to still a further control switch position, to arrange the system for manual control of shaft position, independent of the normal action of the position control mechanism. It is to be understood, however, that the system lends itself readily to providing more or less than ten shaft positions, as desired, for any one shaft, and. that any desired number of shafts may be simultaneously controlled.

Systems capable of accomplishing the above described functions have been constructed and operated heretofore. The present invention relates to improvement in such systems, whereby they may be rendered more compact, more efficient, more accurate, simpler and generally more effective. To this end resort has been had to a concentric type of construction, involving a rotatable outer selector cam drum assembly which.

is motor driven and performs a pawl selection function and being controlled to assume various positions in accordance with the settings of a1 multi-position control switch.

A pawl assembly, comprising a plurality of springpressed pawls for coacting with the selector cam drum assembly, is mounted internally of the'drum assembly, the construction and arrangement of the pawl assembly being such that the pawls remain stationary and are selected for a locking operation in accordance with the final position assumed by the selector cam drum assembly in accordance with the adjustment of the control switch. Internally of both the drum and the pawl assemblies is located a main shaft assembly, comprising a shaft which may be selectively positioned in response to the functioning of the mechanism, and a plurality of lock discs which are free to rotate about the shaft independently of one another, for purposes of preselection or predetermination of shaft positions, and which may be clamped fast to the shaft thereafter. Each of the lock discs is provided with a notch adapted to be secured by one of the pawls to which reference has heretofore been made. After a pawl has been selected by the selector cam drum assembly, in the course of a cycle of operation of the mechanism, the main shaft assembly is rotated relative to the pawl assembly by means of a friction clutch, until the notch in that lock disc which cooperates with the selected pawl is opposite the head of the selected pawl, whereupon the disc is locked by the pawl against further motion, the shaft being then positioned. The shaft may be coupled mechanically to mechanisms of any desiredcharacter which it is reouired to position. A preferred application of the present invention, however, relates to the tuning of radio transmitters, the positionable shafts being then coupled mechanically to the shafts of the tuning elements commonly utilized for selecting communications channels for radio transmitters. 1

Referring now to the drawings, and particularly to Figure 1 thereof, the reference M denotes a reversible drive motor, the specific character of which is of no particular moment but which is selected to be of a minimum dimension. Secured to the shaft 2 of the motor M is a worm gear 3 which meshes with and serves to drive a gear 4 secured by a pin or set screw 5 to a jack shaft 6 .which extends at right angles to the motor shaft 2. The jack shaft 6 extends between a pair of bearings I, 8 secured toor mounted on opposite walls 9, ID of a housing which serves to contain the mechanisms involved in the system of the invention. While the specific character of the bearings I and 8 forms no part of the present invention, the bearing 8 is preferably so constructed as to prevent axial motion of the shaft 6, in known manner.

Secured to the shaft 6 by means of a set screw, or in any equivalent manner, is a worm gear II which serves to transmit motion to the shaft positioning mechanism proper by way of a driven gear I2. Machined on the shaft 6 is a screw thread I3, which performs the function of translating a traveling nut I4, the latter in turn actuating a switching device, which is illustrated in detail in Figure 5 of the drawings, and the function of which will be explained in detail in connection with the circuit diagram of Figure 4.

As will appear when the circuit diagram of Figure 4 is explained in detail, selection of shaft positions is controlled by a manual selector switch having a plurality of contacts, each of the contacts corresponding with a shaft position, which may be predetermined. Upon actuation of the selector switch to initiate a shaft positioning operation the motor M is energized and caused to rotate in a direction such as to cause clockwise rotation of the gear I 2, as viewed in Figure 1. The gear I2 is mounted for rotation on an annular member or hub I5 which may be integral with the main shaft extension I9, and which is internally threaded to accommodate external threads II formed on the end of the main shaft I6. A tapered pin I8, moreover, ex-

tends radially through aligned apertures provided therefor in the annular member or hub I5 and in the shaft I6 to provide a positive coupling therebetween at all times. The end of the annular member or hub I5 which constitutes the shaft extension I9 extends beyond the end plate 20 of the housing, there constituting the positionable shaft of the invention. To the shaft extension IB may be mechanically coupled devices of various character which it is desired to position.

Secured to the forward face of the gear I2 as by means of one or more screws 2| (see Figure 2) is a ratchet wheel 22, which serves as a one way clutch for transmitting motion between the gear I2 and a selector cam drum assembly 23, by means of a spring-pressed pawl 24 which is pivotally mounted on a pin 25 extending from the cylinder 23. In one direction of rotation of the gear I2, specifically clockwise as seen in Figure 1,- some one of the teeth formed in the periphery of the ratchet wheel 22 engages the pawl 24 to drive the drum assembly 23. In'the opposite direction of rotation of the gear 12, on the other hand, and specifically counter-clockwise as viewed in Figure l, the pawl 24 rides over the teeth of the ratchet wheel 22, and provides nomechanical coupling.

The ratchet wheel 22 is provided with an annular recess 26 along the face thereof which rests against the gear I2, the annular-groove formed by the face of the gear I2 and the recess 26 riding on an annular shoulder on the hub I5, this construction serving to prevent lateral play of the gear I2 and of'the ratchet 22 with respect to the hub I5.

A look nut 21 is provided, further, for threadedly engaging a threaded portion 28 of the shaft extension I9 and which serves to retain a spider 29 firmly gripped against the member I5 and immovable with respect thereto. To assure atinsert 3| in a face of the gear I2, the insert 3| being fabricated of friction material and constituting a clutch disc. The arms of the spider 29 taken in conjunction with the annular fibre insert or clutch disc 3| provide a friction or slipping bi-directional clutch for transmitting motion between the gear I2 and the shaft I6.

The selector cam drum assembly 23, which was heretofore referred to as being driven from the gear I2 by means of a uni-directional clutch comprising a ratchet wheel 22 and a pawl 24, is constructed of a plurality of co-axial cylinders and rings, of equal diameter, held together by a plurality of bolts 25 extending therethrough' in a direction parallel to the axis of the shaft I6. Referring specifically to Figures 1 and 2 of the drawings it will be seen that the drum assembly 23 comprises a rear cover plate 32 secured to a face of a hollow cylinder 33 which is rotatable on a ball bearing 34. Stacked to the cylinder 33 is a plurality of thin annular seelctor rings 35, the number of such rings being ten in the exemplified embodiment of the invention, but which may be more or less than ten, as required to suit the exigencies of particular situations. Beyond the selector rings 35is a further hollow cylinder 36 fabricated of metal, as are the rings 35and the cylinder 34, and to the cylinder 36 is secured a further annular member 31' fabricated of electrical insulating material, and to which, at onepoint thereof, is secured a spring conducting member 38, as by means of a screw 39. 'I'hecylinder 36 serves as aforward bearing for the cylindrical structure 23, the inner periphery of the ring 36 bearing rotatably on a portion of the outer periphery of a generally cylindrical structure 40, which is secured to the forward wall 4| of the housing,'as by means of screws 42.

Referring now to Figures 3a and 3b, wherein the structure of the selector rings 35 is clearly illustrated, it will be evident that each of the discs 35 is provided internally with a recess 42a, and having a surface 43 parallel with and set in from the inner periphery of the disc. Connecting the surface 43 with the inner periphery of, each disc 35 is one surface 44 which departs but slightly from the radial and another surface 45 which diverges sharply, and which,'as will appear hereinafter, functions as a cam. The rings 35 will be referred to hereinafter as se lector rings," as descriptive of the function of the rings 35.

The recess 42a of each of the rings 35 is arranged to occupy less than 5 of the total internal periphery of the disc, and the discs when assembled are displaced with respect to one another by a distance equal to of the length. of

the inner periphery, a helical displacement of successive recesses 42a being preferred. Since each recess occupies less than A of the inner periphery and since there are in all ten. discs, it will be clear that after the discs have been assembled there will remain a portion of the interior wall of the assembled drum which corresponds in dimension to, slightly more than A of the inner periphery which is devoid of recesses, as is evident in Figure 317 at 46.

While I haveillustrated and described a structure in which the recesses 42a are displaced one from another, in helical fashion, and wherein individually fabricated rings 35 are assembled to form a drum assembly, I contemplate also a slightly different construction (not shown) wherein a selector cam drum assembly of unitary construction may be employed. the recesses42a being then milled in the interior walls thereof or even out completely through the walls. In such case a different arrangement of the recesses 4211 may be resorted to, specifically after av checkerboard fashion, successive recesses being) displaced by 2, 3, 4 or more elevenths of the inner periphery of the drum. Such an arrangement of the recesses does not affect the general operation of the device, nor the spirit and intent of the invention and may be utilized in the discrete cam ring construction of the selector drum assembly, which is illustrated in the drawings, equally as well as'in the unitary construction of the selector cam drum. '7

The stationary and generally hollow cylindrical frame 40, referred to supra, is cut away for a portion of the wall thereof to accommodate a pawl assembly consisting of a plurality of pivoted pawls 41, which are mounted for limited pivotal movement on a shaft 48 extending across the cut-away parallel to the axis of the cylinder 40 and supported by the walls of the cylinder 40 in fixed relationthereto. The shape of the pawls 41 is clearly shown in Figure 3b of the drawings, each comprising a head or looking portion 49 having atone extremity thereof a generallyradiany extending locking lug 50, slightly tapered.

and a further tail or camming portion 5| adapted to engage a recess 42a of a selector ring 35, or.

fully engaged within a recess 42a and one: of

which isshown riding on the normal inner' pe-- riphery of ring 35. Since the pawls 41 are all similarin shape, and since the recesses 42a,in each of the discs 35 are displaced with respect to. one another it is clear that in no circumstances can more than a single pawl 41 be engaged withla recess 42a at any one time.

Rotatably mounted on the main shaft is a;plu-' rality of shaft positioning discs 52, one ofthe discs 52 being associated with each of the pawls 41. The discs 52 are separated by thin spacer discs or Washers 53, the latter being of smaller diameter than the discs 52, to avoid interference withthe locking lugs 50, and being each provided with a key for interlocking with a keyway-54 machined;

in the shaft l6, Thereby the shaft 16 and the" spacer discs 53 arerendered incapable of relative rotation, but are capable of slight relative axial motion. The discs 52, on the other hand,

may be quite free to rotate on the shaft l5 when released by a locking mechanism, described here?v inafter. Each of the discs 52 is provided witha notch 55 in its outer periphery, WhlCh'iS dimensioned precisely to receive the locking lug 50 of the co-acting pawl 41. Each of the discs 52, as will appear hereinafter, may be positioned with its notch 55 spaced selectively relatively to a zero position of shaft I9, the position of the notch then corresponding with a desired and predetermined position to which shaft l9 may be selectively and automatically positioned in the course of the operation of the system.- When the tails 5| of the pawls 4'! ride on, the inner surfaces of the selector rings 35 the lugs 50 ride free of the discs 52. Rotation of the selectorring drum assembly 23 causes successive ones'of the tails 5| to fall within associated recesses 42m to the slight extent permitted by the lug 50, which rides then'on the outer periphery of its associated positioning disc 52. Rotation of the shaft;

i6 and of the discs 52 locked thereto until a slot 55 coincides with-a lug 53 of that pawl 41, the tail of which has been presented to a'recess 42a,

results finally in the lug 50 falling into andengaging the notch 55, thereby locking thering 52, as well as the shaft l6.

Each of the pawls 41 is individually spring pressed, by means of springs 56 of a multiple cantilever spring assembly secured to the structure,

43, and serving to press the tails 5| of the pawls 47 against the inner periphery of the discs 35'and to press the lugs 58 into engagement with the stop discs 52.

The lock discs 52 may be loosened on the shaft IE to enable positioning of any one or of several thereof in accordance with predetermined desired positions of shaft l9, by loosening the screw 51, which extends internally of the shaft l5 and which may be turned by means of a thumb nut.

5'ia. An end of screw 51 engages with a key 58,

which extends completely through a diametral slot in the shaft I6, and which is capable'of.

axial movement in the slot. The key 58 is provided with ears extending over a ring 59 which may be pressed against the first of rings 52 when the screw 51 is tightened against the key 58, thereby locking the rings 52 firmly on the shaft l5. 1

A limit stop mechanism is provided for lirniij ;v

1. ing the possible motion of the shaft It in the course of a tuning operation, this stop permitting at least a full 360 rotation of the shaft, and providing a definite zero position for the shaft l6 towhich the said shaft is always returned in the course of a shaft positioning cycle, and from which the shaft is positioned to its preselected position. Referring now to Figures 2 and 6 of the drawings, it will be seen that the limit stop mechanism comprises a disc 68 mounted for free rotation on the shaft l6 but comprising a projection 6| which may engage with a stop screw 62 ex,- tending from an aperture in the cylindrical assembly 40. The stop disc 60 further comprises a projection 63, which extends parallel to the shaft I and into the path ofthe key 58. The shaft l8 in one direction of rotation causes the key 58 to impinge upon one face of the projection 83 and carries the disc 60 about the shaft l'8 until the one face of the projection 6| impinges against the stop screw 62. In the opposite direction of rotation of the shaft I6 the opposite face of the projection 63 is engaged by the key 58 and forces the stop disc 60 about the shaft l6 until the opposite face of projection 6| impinges against the stop screw 82. By proper dimensioning of the projections BI and 63, of the screw 62 and of the key 58 it is readily possible to provide free.

rotation of the shaft I'G for 360 or more, while providing a positive zero stop.

Supported on the forward wall 4| of the housing by means of screws 84 is a circuit switch assembly 65, the screws 84 extending, if desired, through slots in the wall 4| to enable adjustment of the position of assembly with respect to the zero position of the shaft l6, thereby assuring proper alignment of the switch assembly 65 with respect to the selector drum assembly, the tuning pawl assembly and the main shaft or look disc assembly.

The circuit switch assembly 65 comprises a ring fabricated of insulating material and containing a co-axial conducting ring 66 secured thereto is well as a plurality of contacts 61 spaced about the insulating ring at intervals of 1 of the circumference, or at positions spaced in correspondence with the positions of the recesses 42a. Radial slots are provided in the insulating ring to enable insertion of conducting lugs 68, which are soldered each to a contact 61 and to which may be soldered or otherwise connected wire leads. To the annular member 31, as has been explained heretofore, at one point thereof is secured the spring contact 38 which provides electrical connection between the conducting ring 66 and a selectedone of the contacts '61, the position of the selector cam assembly 23 determining which one of the contacts 61 shall be in contact with the ring 88.

Circuit diagram Referring now to Figures 4 and 5 of the drawings, .there is illustrated a wiring diagram of the embodiment of the invention forming the subject matter of this specification.

The reference numeral 10 represents a selector switch, which may be positioned remotely from the shaft positioning mechanism proper, and which in the presently described embodiment of the invention comprises 11 positions, ten of which correspond with ten shaft positions and the 11th of which enables manual positioning of the shaft. It will be realized that more or less than 10 shaft positions may be provided for, if desired, without departing from the spirit of and true scope of the invention. The selector arm of the'swltch 10 is connected with one terminal of a source of electrical power ll, shown as positive, and serves to transfer potential from that terminal to the'selected one of the contacts. A pluralityof conductors 12 extend from the respective contacts of the switch 10 to a plurality of shaft positioning units (not shown), and the position offthe selector arm of the switch accordingly mayserve to control a plurality of shaft positions, no limit existing as to the total number of shafts which may be positioned in thepresent system. The conductors 13 serve to'interconnect the contacts of switch 18 with corresponding contacts of the switch assembly 65, and which is illustrated in Figure 5 in conventionalized fashion, the actual structure of the switch assembly 85 having been described hereinbefore.

A relay R is energized when the switches and 18 are in correspondence, the circuit extending from terminal II, over switches 10 and. in series via one of leads l2 and via. the contacts R1, through the coil of relay R and 'back to the source of power 11 via lead 11.

So long as the relay R is energized and contacts R1, R2 and R3 are in the down position the motor M finds no energizing circuit (provided switch remains open) and remains stationary. Operation of the control switch 10 to a new position breaks the circuit to relavv R and normally open contacts R1 as well as contacts R2 and R3 proceed to the open or up position. Thereby a power circuit for the motor M is completed from positive terminalsll, over leads [5, I8, contact R2 through the motor M and thence to contact R3 which is connected to negative terminal H over lead 11. The motor, when energized, rotates, driving clockwise, as seen in Figure 1, the selector cam drum assembly 23 through the one way clutch 22, 24 and also the stop ring discs 52 by means of the slip clutch 29, 3|, and driving the traveling nut H, to the left. The latter in turn actuates a switch bar 18 (Figure 5), but slight movement of which serves to close the contacts 19, 88 of an indicator switch 8|, and the pairs of contacts 82, 83 and 83, 84 of a stop switch 85.

Closure of the indicator switch 8| energizes an indicator lamp 86 at the control position over a circuit extending from the positive one of terminals 'H', lead [5, lead 18, switch 8|, and lead 81 I to the negative terminal H. For the indicator lamp 86 may be substituted a relay, if desired, which may perform various control functions. Alternatively the lamp .86 may be paralleledby such a relay. The relay may be utilized, for example, to remove plate voltage from the tubes of a radio equipment, in the event the present invention is utilized for tuning of such equipment, during the tuning operation.

Closure of the stop switch 85 completes a circuit from the normally hot lead 16 over contact R2 and switch 85 to a now open contact 88 associated with contact R3. Y v V After the traveling nut H has traveled a sufficient distance to assure that the stop ring assembly is zeroized a further switch 14 comprising contacts 81!, 90 (known as the zero limit switch) is closed. Since the zeroizing operation may require a complete rotation of the stop ring assembly, the traveling nut is arranged to close switch 14 at a point adequate to enable a complete rotation of shaft [6, of the cam selector drum assembly and of the switch 65. Thereafter when the switch 65 finds the live lead deriving from the switch Hi, a circuit is completed from;

the positive terminal ll, through switch 10, over 9 the live lead of leads 12 and 13, through selector switch 65, zero limit switch 14, to relay R and thence via leads 11 to the negative terminal 1!. The relay R. being thus energized brings contacts R1, R2, R3 down reversing the potential applied to the motor M, and causing reversal of the direction of its rotation. The selector drum assembly 23 is now at its selected position and the lock ring assembly is zeroized.

Since the selector cam assembly can only be driven clockwise, by virtue of the one way clutch comprising ratchet wheel 22 and pawl 24 the selector cam assembly remains in its selected 150 sitiori and the motor drives only the stop ring drum assembly from its zero position, .by means of the friction clutch 29, 3| until the drum is locked by the selected one of the pawls 91, and

thereafter continues to be driven until the limit switch 14 is opened. This occurrence does not aifect the operation of the motor M, however, since contact R1 is down and provides a circuit for the relay B. As the switch arm 18 re-attains its-initial position, however, the indicator switch 8| is opened, de-energizing the indicator lamp or relay 85. The stop switch 85 is also then opened, breaking the circuit to the motor M and stopping the motor. The cycle of operations is now complete.

Reference is nowmade particularly to Figure of the drawings, wherein is illustrated the structure of a switch bar 18, referred to hereinbefore, and which serves to control various switches involved in the operation of the system. In particular the bar 18 comprises an elongated member fabricated of insulating material, and pivoted on a pin extending through an aperture 96 and driven by a further pin extending down= Wardly from the traveling nut I4 and into an aperture 9I in the bar 18. Riveted or otherwise secured to the bar 18 are two adjacent parallel fiat contact strips 19 and 89,to-each of which is soldered a pigtail. Adjacent the central portion of the bar 18 is secured a fiat conducting member 93 capable of straddling a pair of stationary elongated spring contacts 92 and 84, the latter being secured to a stationary switch bar 92 fabricated of insulating material. Pigtails are soldered'to each of the contacts 82 and 84. The contacts'IS and 89 co-act respectively with elongated spring contacts 89' and 99, secured to the bar 92. The spring contacts 89, 82 and 84 are designed of proper length toassure that but slight movement of the bar 18 toward the bar 92, in response to motion of the traveling nut I4, will result in firm contact being made with the plates 89 and 83 respectively, thus completing circuits which have been heretofore described. The contact 9.0, on the other hand, is considerably shorter than its adjacent contact 89 and is arranged to contact the plate 89 only after the traveling nut I4 has completed roughly half its maxi mum travel. 7 V

A notch 93 is cut in the switch bar 18, adjacent the aperture 9I, which performs the funce tion of engaging a hooked end of a pull bar 94, the other end of the pull bar 94 being secured to a metallic switch member 95 comprising a down wardly depending shoulder 96 in the path of the bar 18 and comprising further a crimp 91 extending into a slot 98, cut into the face of the bar 92. Adjacent to but not in contact with the any reason the relay R will not be energized and the motor M will therefore not be caused to recrimp 91 is a contact bar 99, secured to the bar 92.

The switch member 95 acts in conjunction with the contact bar99 as a safety switch, which is not normally'calle'd upon to, play any part in verse at the point where selection shouldhave,

occurred. The motor M would then continue to drive the selector cam drumassembly, as Well as the'riut I4, until jamming occurred, in the labsence of the safety switch assembly. I With the construction and arrangement described, how: ever, when the bar 18 has arrived at a predetermined point in the. path of its travel, and which is located so that no jamming can occur, the bar 18 presses" against the shoulder 96, and

forcesthe crimp. 91out of the slot 98 and against" the contact bar .99, thereby closing the safety switch I99 (Figure 4), and providing a circuit for the relay R directly from the positive lead 1-5" to the relay R andthence to the negative lead 11. Energization of the relay R causes reversal of the motor M, the stop switch being closed;

and the motor returns them toward its starting point. Just prior to reaching the starting point, and with switches 85 and 14 still closed, the notch 93 in switch arm 18 reaches the hook in pull rod 94 and destroys the contact between bar 99 and switch contact 95, reinstating the crimp 91 in the slot or groove 98, which is equivalent to an opening of switch I in Figure 4. Opening of switch I99 de-energizes the relay R and thus again reverses the direction of rotation of the motor M and initiates a further selecting operation. The safety switch I09 'thusoperates to cause a continually repeated cycling action to take place in the system until such time as selection takes place, preventing damageto the mechanism due to temporary prevention of selection.

Prevention of completion of a-selection'cycle may be caused by modification ofthe position of the controlswitch 19 during th selection'cycle. If, for example, position number I9 were selected by control switch 19, and the selection Operation Proceeding now to a description of the operae tion of the system as a whole, any particular switch station at control switch 10 may be made to correspond with any selected shaft position by selecting the particular switch station, and after the pawl 41 corresponding with that switch station has locked its co-acting lock ring 52, re-

leasing the thumb nut 51a to permit relative. movement of the selected lock ring 52 and the shaft IS. The shaft I6 is then turned to the desired position by manual manipulation of the knob II, which is secured to the shaft I E'b'y'. means of a set screw I 92. manipulation the selectedstop disc 52 remains stationary since it is held by an engaging pawl 41. All the other stop discs 52, however, rotate with the shaft and maintain their previously set -positions, being separated from the selected stop disc 52 by spacer discs or washers 53 which are During this manual l1 keyed to the shaft I6 and which prevent transfer of motion from one stop disc to-another. After the shaft I6, or the shaft extension |9, has been rotated to the desired position the stop discs 52 may be locked by turning the thumb nut 51a clockwise (Figure 2). a

By repetitive operations such as explained in the preceding paragraph eachof the switch positions of the switch may be made tocorrespond with a desired shaft position. The shaft l9 maybe connected with or mechanically coupled to control or tuning elements of a radio transmitter or other device, in a manner which is obvious per se, and the control switch 10 then utilized for precise remote control of tuning. Many other operationsmay obviously be performed which require the precise positioning of selves to those skilled in the art.

After the desired shaft positions have been set up any desired one of the pre-established shaft positions may be established automatically by manipulation of the control switch 10. When the operator selects a new position the circuit of the normally energized relay R is broken, starting the motor M in clockwise rotation, and the gear l2 in similar rotation.

The traveling nut l4 moves to the left closing the indicator switch 8| and the stop switch 85 and the clockwise rotation of the gear-l2 causes rotation of the selector ring drum assembly 23. As the drum assembly 23 rotates, that one of the pawls 41 which was engaged with a stop ring 52 is cammed out of engagement by the action of the surface 45 against the tail 5|. The stop ring assembly and the main shaft l5 are one or more shafts, and which will suggest them-'- now free to'rotate and are caused to do so by the action of the friction disc 3| against the spider 29, the latter slipping until the previously selected stop disc 52 has been released.

As the motor continues to turnthe main shaft reaches its zero position, where it is stopped by the action of the projection fil when it impinges against the-stop screw 62, the spider 29 then proceeding to slip. The selector cam drum as-- sembly 23, however, continuesto rotate and the switch arm 18 to pivot. Shortly after the main shaft has been zeroized the zero limit switch 14 is closed, which prepares a circuit for the relay R, that circuit being closed when the switch arm of switch 65 finds'that one of its contacts which is wiredto the selected contact of control switch 10. Energization of relay R operates a series of associated contacts R1, R2, R3 which provides-a 1 circuit for the relay R inparallel to the switch 14, and which also serve to reverse the voltage applied to the motor M, causing same to reverse.

Dur ng the course of the rotation of the selector cam drum assembly various of the pawl tails 5| have dropped partially into associated recesses'"42a and have been cammed out again.

When selection is complete, at the time of motor reversal, the tail of a particular pawl 12 which rests against the surface 44 associated with the selected recess 42a.

The main shaft l6 and the stop rings 52 are driven by the friction clutch |2, 29, in counterclockwise rotation until the head or lug 50 of the selected pawl 41 drops within the notch'55 of the associated stop ring 52, in response'to the pressure of spring 56, after which the, main shaft I6 is locked, the clutch |2, 29 slippingto enable continued rotation of the motor M.

The switch bar 18 has been returning to its starting position during reverse rotation of the motor M, opens the zero limit switch 14, which has no effect on the operation of the system,

since the paralleling switch comprising contact'f R1 is closed. The switch bar 18 continues its return motion, until the stop switch and the indicator switch 8| are opened, when the motor M becomes deenergized and the operation is completed.

Should completion of selection be prevented by reason of a displacement of the control. switch 10 in the course of a shaft positioning operation but prior to completion of the operation,

the switch arm 18 will continue to the limit of its travel, where it will encounter and close the safety switch I00, causing reversal of motor M.

That such failure may take place due to no defect of the mechanism will become apparent when it is considered that the control switch I0 may be operated to select new shaft positionsat any time, and that one or more control operations may conceivably take place in the course of a cycle of operations of the mechanism.

When the motor, in reversed direction, ap-

proaches its initial position, but before it becomes de-energized, the safety switch I00 ,is opened by the action of pull bar 94, and the system embarks upon another selection cycle.

Should it be desired to position the shaft I6 manually, the control switch 10 is turned to position II, which corresponds with a point 46 on the inner periphery of the selector cam drum assembly which contains no recess 42a. Thereby, all thepawls 41 are retained out of engagement with the stop discs 52, and the shaft ll remains free except for such friction as may be introduced by the friction clutch |2, 29. Rotation of knob then enables corresponding free rotation of the shaft I6 within the limits'set V by the limit stop mechanism 60 (Figure 6).

Having described one specific embodiment of the invention, it is to be understood that modifications of various constructional features. as

well as of' the arrangement and combination of various of the elements of the system, maybe resorted to without departing from the spirit and true scope of the invention, which is defined in the appended claims.

What I claim and desireto secure by Letters Patent of the United States of America is:

1. Shaft positioning apparatus com rising a shaft positionable to any one of a plurality of lock one of said stop discs' only, said shaft and said pawls being at least in partlocated interior-'1 ly of said'selector'cam drum, 9, multi-contact' selector switch having a finder, arm secured to said selector cam drum, a multi-contact selective control switch having contactsponnected one for one with, contacts of said selector switch, a drive system for rotating said selector cam drum, a unidirectional clutch means coupling said drive system to said selector cam drum, means responsive to a predetermined operation of said control switch for initiating a cycle of operation of said drive system in a direction to accomplish rotation of said selector cam drum by said unidirectional clutch, means for terminating operation of said drive means when said finder contact reaches a contact of said-selectorswitch which is connected to a selected contact'of said control switch, and means operative only upon failure of said finder contact to reach a contact of said selectorswitch which is connected to a selected contact of said control switch for initiating a repetition of said cycle of operation, said last means responsive to attainment-by said selector cam drum of a limit position duringthe first mentioned cycle of operation. l

2. Shaft position apparatus comprising a shaft positionable to any one of a plurality of predetermined positions, a selector cam drum assembly, a plurality of stop discs positionably secured to said shaft, a plurality of pawls selectable one by one by said selector cam drum assembly and each'operable when selected to lock one of said step discs only, said shaft being" at least in part located interiorly of said selector cam drum, a control switch, means for initiating a positioning operation of said selector cam drum in response to control action of said control switch, and means responsive to failure of said positioning operation for initiatin a further positioning op eration.

3. Shaft positioning apparatus comprising a multi-contact selector switch having a finder contact, a multi-contact control switch having contacts connected one for one with the contacts of said multi-contact selector switch, a selector cam drum, a drive system for driving said selector cam drum, unidirectional clutch means coupling said drive system to said selector cam drum, means responsive to operation of said control switch to select a predetermined contact of said control switch for initiating operation of said drive system in a direction to accomplish movement of said selector cam drum via said unidirectional clutch means, a safety switch operable in response to attainment of an unsafe position by said selector cam drum means for terminating operation of said drive system in said a direction when said finder contact reaches a contactof said selector switch selected by said control switch or said safety switch operates, a shaft, a plurality of discs releasably secured to said shaft, a lock notch formed in each of said discs, means for locking said discs to said shaft, said selector cam drum having drum cam recesses accessible interiorly thereof and at least in part surrounding said discs, and a plurality of pawls each having a head portion for securing a lock notch of one only of said discs and a tail portion spring pressed to drop into one only of said recesses, and means operative following said termination of operation of said drive system in said a direction for rotating said shaft toward a position determined by the position of said selector cam drum.

4. Shaft positioning apparatus comprising a shaft positionable to any of a plurality of predeterminable positions, a rotatable selector cam drum assembly, a plurality of stop discs positionably secured to said shaft, a plurality of pawls selectable one by one by said selector cam 14? drum assembly for different. rotative positions thereof :and each, operablewhen selected to lock one of said stop. Idiscs only, said shaft being at least-in part located interiorly 'of said selector cam drum, 2; multi-contactselectorswitch, hav- 111g, a finder arm secured to said selector cam drum, a multi-contact selective control switch having contacts connectedone for one with contacts of said selector switch arm, a drive system for rotating said selector cam drum, a unidirectional clutch means coupling said drive system to said selector cam drum, means responsive to a predetermined operation of said control switch for initiating operation of said driveisystem in a. direction to accomplish rotation of said selector cam drum by said unidirectional clutclrza safety switch operated in response topredetermined rotation of said selector cam drum, and means for terminating operation of said drive system in said a direction when said finder contact reaches a contact of selector switch which is connected to a selectedcontact of said control switch, or whensaid safety switch operates and for initiating a further operation of said drive system reversely to, said a'direction.

5, Shaft positioning apparatus comprising a shaft positionable in any one of a plurality of predeterminable positions, a hollow rotatabl'eselector cam drum encompassing said shaft, a plurality of stop discs positionably secured to said shaft, a plurality of pawls selectable one by one by said selector cam drum in response to increments of rotation thereof, each of said pawls associated with one of said stop discs, and operable when selected to lock one of said stop discs only in a predetermined position, a multi-contact selector switch having a plurality of contacts and a contact finder arm, means for selectively applying potential to said contacts, first drive means for rotating said selector cam drum and comprising a unidirectional clutch, said unidirectional clutch comprising a ratchet wheel and pawl, reversible drive means for rotating said shaft comprising a slipping bi-directional clutch, means responsive to potential applied to a selected one of said contacts for actuating said first drive means for rotating said selector cam drum to a selected position determined by the selected contact, thereby to select one of said pawls, and for actuating said reversible drive means for rotating said shaft to a predetermined zero position, means operative only after said shaft has been rotated to said -zero position and said selector cam drum to said selected position for reversing both said drive means, whereby said unidirectional clutch is decoupled and said shaft is rotated reversely via said slipping clutch, and means responsive to arrival of said shaft to a position predetermined by selection of said pawl, while rotating reversely, for locking said shaft against further motion while said slipping clutch continues to slip.

6. Shaft positioning apparatus, comprising, a shaft positionable to any one of a plurality of predeterminable positions, a selector cam drum assembly, a plurality of stop discs positionably secured to said shaft, a plurality of pawls selectable one by one by said selector cam drum assembly and each operable when selected to lock one of said stop discs only, a multi-contact selector switch having a switch position determined by the position of said selector cam drum, a control switch for selecting contacts of said multicontact selector switch, a reversible drive motor, a unidirectional clutch coupling said drive motor and said selector cam drum assembly, a bi-directional slipping clutch for coupling said motor and said shaft, means responsive to selection of a predetermined contact of said multi-contact selector switch by said control switch for initiating rotation of said motor in a direction to drive said unidirectional clutch and thereby said selector cam drum assembly in a first predetermined direction and to drive said shaft via said bi-directional slipping clutch in said first predetermined direction toward a zeroized position, a safety limit switch operable in response to attainment by said selector cam drum assembly of a predetermined unsafe position, and means responsive to attainment of said selector cam drum assembly of either said unsafe position or a position corresponding with said predetermined contact of said multi-contact selector switch for effecting reversal of said motor. 7. A shaft positioning system comprisin a plu rality of pawls, a shaft positionable to any one of a plurality of predeterminable positions, a pawl selector for selecting one of said pawls, stop discs secured to said shaft, each of said pawls selecting a different one of said stop discs when selected by said pawl selector, means for zeroizing said shaft in one direction and thereafter cycling said pawl selector in said one direction to select 16 a predetermined pawl, means thereafter actuating said stop discs in a reverse direction to engage said predetermined pawl, and means responsive to failure of said pawl selector to select said predetermined pawl for recycling said pawl selector to select a predetermined pawl.

WILLIAM L. WORTHEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,257,198 Duncan Feb. 19, 1918 2,164,309 Collins July 4, 1939 2,216,272 Kaye Oct. 1, 1940 2,293,355 Olson Aug. 18, 1942 2,320,808 Van Lammeren et a1. Jan. 1, 1943 2,378,941 May June 26, 1945 2,391,470 May Dec. 25, 1945 2,553,951 Stamper May 22, 1951 2,574,603 Uhlig Nov. 13, 1951 FOREIGN PATENTS Number Country Date 385,672 Great Britain Jan. 5, 1933 

